Sulfonate-functional polyester polyols

ABSTRACT

Sulfonate-functional polyester polyols are derived from reactants comprising an unsaturated polycarboxylic acid or derivative thereof, a polyol, a lactone, and a sulfonating agent. The unsaturated polycarboxylic acid or derivative is substantially free of sulfonate functionality, thereby providing sulfonate-fimctional polyester polyols having low color. The sulfonate-functional polyester palyols are suitable for use, for example, in the manufacture of water-dispersible polyurethanes and polyurethanes used as dispersants for particulate materials, for example, in magnetic recording media.

FIELD OF THE INVENTION

The present invention relates to polyester polyols. More specifically,the present invention relates to sulfonate-functional polyester polyolsand polyurethanes made therefrom.

BACKGROUND OF THE INVENTION

Polyester polyols are polymers containing at least two hydroxyl groupsand at least two ester groups. Typically, polyester polyols are used asreactive intermediates in the manufacture of other polymers such aspolyurethanes and polyesters. In addition, polyester polyols are used asdiluents in the formulation of polymer-containing products to improveflexibility and other properties. Polyurethanes made using polyesterpolyols have a variety of uses including, for example, the manufactureof fibers, coatings, elastomers, foams, adhesives, and sealants.

In certain cases, such as in the manufacture of water-dispersiblepolyurethanes or polymers used as dispersants for polar materials, forexample, dyes and pigments, the incorporation of ionic functionalityinto the polyester polyol can be advantageous. In the field ofwater-dispersible polyurethanes, U.S. Pat. No. 5,929,160, discloses achain extended sulfopolyester polyol made by reacting asulfopolycarboxylic acid or ester with a polyol to produce asulfopolyester polyol, and then chain extending the sulfopolyesterpolyol by an esterification reaction with a lower aliphatic lactone.Sulfonate-containing cationic dyeability modifiers for use in polyestersand polyamides are disclosed in U.S. Pat. No. 6,312,805. In the field ofmagnetic recording media, U.S. Pat. No. 5,695,884, discloses athermoplastic polyurethane composition wherein the polyurethane has ametal sulfonate group, and teaches that it is preferred that thepolyester polyol is prepared by the use of a dicarboxylic acid having ametal sulfonate group as a part of the acid component. The dicarboxylicacid having a metal sulfonate group can be either an aromaticdicarboxylic acid or an aliphatic dicarboxylic acid. Examples of thedicarboxylic acid component having a metal sulfonate group includesodium 5-sulfoisophthalate, potassium 5-sulfoisophthalate, sodium2-sulfoterephthalate, and potassium 2-sulfoterephthalate.

The use of sulfonated acids such as 5-sulfoisophthalic acid in themanufacture of polyester polyols can cause problems because therelatively high temperatures needed to react the acid with the polyolcan cause discoloration, that is, high color, in the product. High coloris generally undesirable for aesthetic reasons, particularly when thepolyester polyol is used in a coating application. Furthermore, when thesulfonate-functional dicarboxylic acid is aromatic, for example, in thecase of sulfoisophthalic acids, the sulfonate group often has restrictedmobility due to its bonding to the rigid phthalic acid moiety. Therestricted mobility can adversely affect the dispersing properties ofthe corresponding polyurethane.

It would be desirable to have improved sulfonate-functional polyesterpolyols that can be prepared from carboxylic acids that do not havesulfonate functionality.

SUMMARY OF THE INVENTION

The present invention provides sulfonate-functional polyester polyolsthat are derived from reactants including an unsaturated polycarboxylicacid or derivative thereof, a polyol, a lactone, and a sulfonatingagent, wherein the unsaturated polycarboxylic acid or derivative thereofis substantially free of sulfonate-functionality. The invention includespolyurethanes prepared from the polyols of the invention.

By virtue of the present invention, it is now possible to providesulfonate-functional polyester polyols that have low color. As a result,the sulfonate-functional polyester polyols of the present invention canbe used, for example, as additives or reactive diluents to improveproperties of compositions, or as reactive intermediates in themanufacture of polyurethanes having low color. Typical end uses for thepolyurethanes of the present invention include, for example,water-dispersible polyurethanes, coatings, foams, fibers, sealants,adhesives and dispersants for dyes, pigments and particulate materials,for example, magnetic particles used in magnetic recording media.

The present invention also includes a process for manufacturingsulfonate-functional polyester polyols, the process including the stepsof: reacting an unsaturated polycarboxylic acid or derivative thereofwith a polyol to make an unsaturated polyol; reacting the unsaturatedpolyol with a sulfonating agent to form a sulfonate-functional polyol;and reacting the sulfonate-functional polyol with a lactone to providethe sulfonate-functional polyester polyol. Advantageously, in accordancewith the present invention, the reaction of the unsaturatedpolycarboxylic acid or derivative thereof and the polyol can beconducted at an elevated temperature, that is, high enough to promotethe reaction, while avoiding color formation since thesulfonate-functionality is not introduced until after the unsaturatedpolyol is formed. Then, the sulfonation can be conducted at a lowertemperature sufficient to promote the sulfonation, without promoting theformation of color in the sulfonate-functional polyol.

DETAILED DESCRIPTION OF THE INVENTION

The process of the invention prepares a sulfonate-functional polyesterpolyols from reactants including an unsaturated polycarboxylic acid orderivative thereof, a polyol, a lactone, and a sulfonating agent.

The unsaturated polycarboxylic acid or derivative thereof suitable foruse in accordance with the present invention advantageously has at leasttwo carboxyl groups and from about 4 to about 36 carbon atoms, andpreferably from about 4 to about 8 carbon atoms. The unsaturatedpolycarboxylic acid has at least 1, advantageously 1 to about 4,ethylenically unsaturated bonds. As used herein, the term “derivative”of the polycarboxylic acid include the corresponding anhydrides, esters,half-esters, carbonyl chlorides, and mixtures thereof. Dicarboxylicacids are preferred. Examples of preferred dicarboxylic acids include,for example, maleic acid, fumaric acid and itaconic acid. An especiallypreferred ethylenically unsaturated dicarboxylic acid or derivative ismaleic acid or maleic anhydride. The amount of the unsaturatedpolycarboxylic acid used to make the sulfonate-functional polyesterpolyol is not critical to the present invention and is advantageouslyfrom about 0.5 to about 20 weight percent based on the total weight ofreactants used to make the sulfonate-functional polyester polyol.Preferably, the amount of the unsaturated polycarboxylic acid is fromabout 20 to about 80 weight percent, based on the total weight of theunsaturated polycarboxylic acid and polyol used to make the unsaturatedpolyol. Mixtures of unsaturated polycarboxylic acids can be employed.Several unsaturated polycarboxylic acids and derivatives thereofsuitable for use in accordance with the present invention arecommercially available.

In accordance with the present invention, the unsaturated polycarboxylicacid or derivative thereof is substantially free of sulfonatefunctionality. As used herein, the term “sulfonate functionality” or“sulfonate-functional” means a —SO₃M group where M is a positivelycharged counterion, for example, an ammonium or alkali metal ion. Theterm “sulfonate-functional group” is also referred to in the art assulfonyl group, sulfo group, sulfonate group, or sulfonic acid group orsalt thereof. As used herein, the term “substantially free” means lessthan 0.1, preferably less than 0.05, and more preferably less than 0.01,sulfonate group equivalents per mole of unsaturated polycarboxylic acid,on average. Stated another way, on average, less than 10 percent,preferably less than 5 percent, and more preferably less than 1 percentof the molecules in the unsaturated polycarboxylic acid startingmaterial will have sulfonate-functionality.

The polyol suitable for use in accordance with the present invention hasat least two hydroxyl groups. In a preferred aspect of the invention,the polyol has from about 2 to about 40 carbon atoms. The polyolpreferably is saturated. Aliphatic diols having from about 2 to about 12carbon atoms are preferred. Examples of suitable polyols include1,2-ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol,2,2-diethyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol,2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol,1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,2,2,4-trimethyl-1,6-hexanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol,3-methyl-1,5-pentanediol, 1,2-cyclohexanediol,1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, p-xylenediol, and2,2,4,4-tetramethyl-1,3-cyclobutanediol. Especially preferred polyolsare 1,4-butanediol and 1,6-hexanediol. In another aspect of theinvention, a polyether glycol can be used as the polyol. Examples ofpreferred polyether glycols include, for example, polyoxyethylenepolyols, polyoxypropylene polyols, and poly(oxypropylene-oxyethylene)polyols, preferably having a number average molecular weight of fromabout 200 to about 6000. Suitable polyether glycols are commerciallyavailable, for example, from The Dow Chemical Company under thetrademarks VORANOL™ polyols or CARBOWAX™ polyols. Mixtures of polyolscan be employed.

The amount of polyol used in preparing the sulfonate-functionalpolyester polyol of the present invention is not critical andadvantageously is from about 0.5 to about 50 weight percent, andpreferably from about 2 to about 40 weight percent, based on the totalweight of the reactants used to make the sulfonate-functional polyesterpolyol. More preferably, the amount of the polyol is from about 20 toabout 80 weight percent, based on the total weight of the unsaturatedpolycarboxylic acid and polyol used to make the unsaturated polyol.Several polyols suitable for use in accordance with the presentinvention are commercially available.

The lactone suitable for use in accordance with the present inventionadvantageously has from about 3 to about 20 carbon atoms. Examples ofsuitable lactones include: caprolactone; t-butyl caprolactone;zeta-enantholactone; delta-valerolactones;monoalkyl-delta-valerolactones, such as the monomethyl-, monoethyl-, andmonohexyl-delta-valerolactones, and the like; monoalkyl, dialkyl, andtrialkyl-epsilon-caprolactones such as the monomethyl-, monoethyl-,monohexyl-, dimethyl-, di-n-hexyl, trimethyl-,triethyl-epsilon-caprolactones, 5-nonyl-oxepan-2-one, 4,4,6- or4,6,6-trimethyl-oxepan-2-one and the like; 5-hydroxymethyl-oxepan-2-one;beta-lactones, for example, beta-propiolactone; beta-butyrolactone orpivalolactone; gamma-lactones, such as gamma-butyrolactone; dilactones,such as lactide; dilactides; glycolides, such as tetramethyl glycolides,and the like; dioxanones, such as 1,4-dioxan-2-one, 1,5-dioxepan-2-one,and the like. The lactones can be the optically pure isomers or two ormore optically different isomers or other mixtures. Epsilon-caprolactoneand its derivatives, for example, methyl-epsilon-caprolactone, and otherseven membered ring lactones are especially preferred. The amount of thelactone used in the sulfonate-functional polyester polyol of the presentinvention is preferably from about 10 to about 98.5 weight percent, andmore preferably from about 40 to about 90 weight percent, based on thetotal weight of the reactants used to make the sulfonate-functionalpolyester polyol. Several lactones for use in accordance with thepresent invention are commercially available.

The sulfonating agent suitable for use in accordance with the presentinvention can be any compound capable of impartingsulfonate-functionality to the unsaturated polyol. Sulfonating agentscan be organic or inorganic. Preferably, the sulfonating agent is aninorganic compound having an oxygen atom bonded to a sulfur atom.Preferably, the sulfonating agent comprises one or more bisulfites orone or more metabisulfites or mixtures thereof. Preferred sulfonatingagents are the ammonium and alkali metal bisulfites and alkali metalmetabisulfites. More preferred sulfonating agents are sodium bisulfiteand sodium metabisulfite. Other preferred sulfonating agents includelithium bisulfite, lithium metabisulfite, potassium bisulfite, potassiummetabisulfite, ammonium bisulfite and ammonium metabisulfite. Othermaterials, such as inorganic salts, for example, sodium hydroxide, canbe optionally included to control the reactivity and pH of thesulfonating agent. The amount of sulfonating agent used to make thesulfonate-functional polyester polyols of the present invention is notcritical, but preferably is sufficient to sulfonate all of the doublebonds in the unsaturated polyol. Advantageously, the amount is fromabout 0.5 to about 20 weight percent, and preferably from about 2 toabout 16 weight percent, based on the total weight of the reactants usedto make the sulfonate-functional polyester polyol. More preferably, theamount of the sulfonating agents is from about 15 to about 50 weightpercent, based on the total weight of the unsaturated polycarboxylicacid, polyol and sulfonating agents used to make thesulfonate-functional polyol. Several suitable sulfonating agents arecommercially available.

The processes used to make the sulfonate-functional polyester polyols ofthe present invention can be batch, continuous, or semi-continuous usingconventional equipment, the details of which are known to those skilledin the art.

The first step of the process comprises contacting the unsaturatedpolycarboxylic acid or derivative thereof with the polyol under reactionconditions sufficient to form an unsaturated polyol. In the case ofunsaturated anhydrides, such as maleic anhydride, the first step occursin two stages. In the first stage, ring opening of the anhydride occursand one molecule of the polyol, for example, 1,6-hexanediol, is attachedto form an ester on one end of the anhydride residue and an acid orcarboxylate on the other end. This first stage can be conducted at arelatively low temperature, for example, at from about 60 to about 160°C., or higher if desired. Preferably, the first stage is conducted inthe absence of a solvent and in the presence of a catalyst such as, forexample, butyl tin hydroxide oxide. In the second stage of the firststep, another molecule of the polyol is condensed with the acid groupremaining on the anhydride residue to form a second ester group on theunsaturated polyol. Typically, the second stage requires a highertemperature to complete the reaction, for example, from about 160 toabout 240° C. Preferably, the second stage is also conducted in theabsence of a solvent. The first and second stages of the first step ofthe reaction can be conducted in discrete steps, but preferably areconducted in a common step in the same reaction vessel.

In the second step of the process, the unsaturated polyol is contactedwith the sulfonating agent under reaction conditions sufficient to forma sulfonate-functional polyol. Sulfonation of the unsaturated polyol isadvantageously carried out using a slight stoichiometric excess of thesulfonating agent. The sulfonation advantageously is carried out in asuitable solvent such as water. The temperature of the sulfonation stepadvantageously is from about 10 to about 120° C., preferably from about25 to about 100° C. The sulfonation also can be optionally assisted, forexample, by passing air through the reaction medium or by peroxides suchas hydrogen peroxide, benzoyl peroxide, or t-butyl hydrogen peroxide.Preferably, water is removed from the sulfonate-functional polyolreaction product after the sulfonation is completed. Optionally, thesulfonation can be conducted in the presence of one or more solventsthat form an azeotrope with water, such as, for example, toluene, inorder to enhance the subsequent removal of water from the product, orthe azeotrope can be added after all or part of the sulfonation reactionhas occurred.

In the third step of the process, the sulfonate-functional polyol iscontacted with the lactone under reaction conditions sufficient to formthe sulfonate-functional polyester polyol. Advantageously, this step(also referred to in the art as ring-opening polymerization or chainextension) is conducted at a temperature of from about 25 to about 200°C., preferably from about 80 to about 180° C., in the presence of acatalyst. Examples of catalysts that can be used to prepare thesulfonate-functional polyester polyol are those known to persons skilledin the art of polyester preparation, illustrative of which aredibutyltin oxide, antimony oxide, tin oxide, tin octoate, organotinalkanoates, titanium alkoxides, aluminum alkoxides, aluminum oxidealkoxides, alkali metal salts or salts of manganese, cadmium, magnesium,zinc, cobalt, tin, and the like. Advantageously, the reaction isconducted in the absence of a solvent. The molecular weight of thesulfonate-functional polyester polyol can be controlled by the number oflactone molecules that are polymerized onto the sulfonated polyol.

The pressures at which the reaction steps of the present invention areconducted are not critical and advantageously range from about 0.1 toabout 3 atmospheres (absolute). Similarly, the time required for eachstep is not critical and advantageously ranges from about 0.5 to about20 hours for each of the first step and second step and from about 2 toabout 100 hours for the third step.

If desired, additional materials can be used to makesulfonate-functional polyester polyols of the present invention in orderto impart desired properties. For example, other polyol initiators,antioxidants, stabilizers, acid scavengers, plasticizers, coalescingsolvents, reactive diluents, pigments and fillers can be employed.Further details concerning suitable reaction conditions, equipment,reactants, additives and catalysts can readily be determined by thoseskilled in the art.

Preferably, the sulfonate-functional polyester polyols of the presentinvention have low color. Advantageously, the color on theplatinum-cobalt scale is less than 50, preferably less than 25 and morepreferably less than 15. As used herein, the term “color” means thecolor as measured according to the method set forth in ASTM-D-1209.Without being bound to any particular theory, it is believed that coloris formed by exposure of the sulfonate group to elevated temperatures.In accordance with the present invention, exposure of the sulfonategroup to elevated temperatures can be avoided because the unsaturatedpolycarboxylic acid or derivative thereof used in the first reactionstep is substantially free of sulfonate functionality. Thus, thereaction of the unsaturated polycarboxylic acid or derivative thereofwith the polyol can be conducted at an elevated temperature sufficientto promote the formation of the unsaturated polyol, while thesulfonation reaction can be conducted at a lower temperature effectiveto promote the formation of the sulfonate-functional polyol, but avoidthe formation of color. Preferably in accordance with the presentinvention, the maximum temperature of the reaction step wherein theunsaturated polyol is reacted with the sulfonating agent is at leastabout 20° C., preferably at least about 30° C., less than the maximumtemperature at which the reaction of the unsaturated polycarboxylic acidor derivative thereof and the polyol is conducted.

In one aspect of the invention, the sulfonate-functional polyesterpolyol can be represented by the formula:

where:

-   R¹ is a trivalent hydrocarbon group having from about 2 to about 14    carbon atoms;-   M⁺ is a positively charged counterion;-   x is from about 2 to about 80;-   n is from about 2 to about 17; and-   R² is a divalent hydrocarbon group having from about 2 to about 12    carbon atoms.    Preferably, the sulfonate-functional polyester polyol described by    the formula above has a color of less than about 50.

Preferably, R¹ is an aliphatic hydrocarbon group having from about 2 toabout 8 carbon atoms. More preferably, R¹ is an alkyl group having fromabout 2 to about 4 carbon atoms. Preferably R² is an aliphatichydrocarbon group having from about 2 to about 12 carbon atoms. Morepreferably R² is a residue of an aliphatic diol having from about 4 to1,5-diisocyanate, diphenylmethane 2,4′ diisocyanate, diphenylmethane4,4′-diisocyanate, dicyclohexylmethane diisocyanate, isophoronediisocyanate are suitable for this purpose. Preferred polyisocyanatesare aromatic diisocyanates such as toluene 2,4-diisocyanate, toluene2,6-diisocyanate and mixtures thereof, available, for example, from TheDow Chemical Company, under the tradenames VORANATE* T-80, ISONATE*M-124 and ISONATE M-125. Mixtures of polyisocyanates can be employed.The amount of polyisocyanate used in the polyurethane is not critical tothe present invention, but advantageously corresponds to a urethanegroup concentration of about 100 to about 10,000 equivalents per 10⁶grams of polyurethane.

Likewise, the amount of sulfonate-functional polyester polyol is notcritical and is dependent on the desired properties of the polyurethane.Advantageously, the amount of sulfonate-functional polyester polyol isselected to provide a sulfonate group concentration of about 10 to about5,000, preferably from about 10 to about 3000, equivalents per 10⁶ gramsof polyurethane, based on the sulfonate group having a mass of 80 g/mol,that is, excluding the mass of the counter ion.

In addition to the sulfonate-functional polyester polyol, other polyolsmay be incorporated into the polyurethane in order to provide desiredproperties. Properties that can be varied include, for example,ductility, water uptake, tensile strength, modulus, abrasion resistance,minimum film formation temperature, and glass transition temperature.Longer chain polyols tend to provide materials that are more ductile andhave a lower glass transition temperature (“Tg”), whereas shorter chainpolyols tend to contribute to high modulus, and a higher Tg. The otherpolyol that is different from the sulfonate-functional polyester polyolis preferably selected from the group consisting of polyester polyols,polyether polyols, polycarbonate polyols, hydrocarbon polyols, copolymerpolyols prepared from at least 2 monomers used to make these homopolymerpolyols, and mixtures thereof. The polyester polyols are preferablypredominantly linear polymers having terminal hydroxyl groups,preferably those having two terminal hydroxyl groups. The acid number ofthe polyester polyols preferably is less than about 10, and morepreferably is less than about 3. The polyester polyols can be preparedby esterifying aliphatic or aromatic dicarboxylic acids of from about 4to about 15, preferably about 4 to about 8, carbon atoms with glycols,preferably glycols of from about 2 to about 25 carbon atoms, or bypolymerizing lactones of from about 3 to about 20 carbon atoms, thedetails of which are about 6 carbon atoms. Preferably x is from about 2to about 40. Preferably n is 3 to about 6. Most preferably, n is 5. Thevalues of x and n are average values.

Advantageously, the molecular weight of the sulfonate-functionalpolyester polyol of the present invention is from about 450 to about10,000 grams per mole (“g/mole”). Preferably, the molecular weight isfrom about 500 to about 5,000 g/mole. As used herein the term “molecularweight” means number average molecular weight. Techniques fordetermining the number average molecular weight are known to thoseskilled in the art, for example, end group analysis (OH titration) gelpermeation chromatography or high pressure liquid chromatography.Advantageously, the sulfonate equivalent weight is from about 250 toabout 5,000 g/mole. In a preferred aspect of the invention, thesulfonate-functional polyester polyol contains one sulfonate equivalentper molecule. The sulfonate equivalent weight can be determined bydividing the average number of sulfonyl groups per molecule into thenumber average molecular weight.

The sulfonate-functional polyester polyols of the present invention havea variety of uses. For example, the sulfonated polyester polyols can beused as additives in compositions to improve properties such asdispersability in aqueous systems, dispersability of particulatematerials, for example, pigments or metal particles, compatibility withother materials or reduced viscosity. In addition, thesulfonate-functional polyester polyols can be used as reactive diluentsin a variety of compositions and polymers such as, for example, acrylicpolymers and polyesters, in order to improve flexibility. Anotherexample of a use for the sulfonate-functional polyester polyols of thepresent invention is as a dyeability modifier for incorporation intopolyesters and polyamides such as disclosed in U.S. Pat. No. 6,312,805.

In a preferred aspect of the present invention, the sulfonate-functionalpolyester polyols are used to make polyurethanes. In a broad sense, thepolyurethanes of the present invention comprise the reaction product ofa polyisocyanate and the sulfonate-functional polyester polyol.Advantageously, the polyisocyanate is an aliphatic, cycloaliphatic oraromatic diisocyanate having from about 6 to about 30 carbon atoms andat least two isocyanate groups per molecule. Compounds such as toluene2,4-diisocyanate, toluene 2,6-diisocyanate, meta- andpara-tetramethylxylene diisocyanate, 4-chlorophenylene 1,3-diisocyanate,naphthylene 1,5-diisocyanate, hexamethylene 1,6-diisocyanate,hexamethylene 1,5-diisocyanate, cyclohexylene 1,4-diisocyanatetetrahydronaphthylene known to those skilled in the art. Polyesterpolyols made with lactones are also referred to in the art aspolylactone polyols. The polyether polyols are preferably predominantlylinear polymers that have terminal hydroxyl groups, contain ether bondsand have a molecular weight of from about 600 to about 4000, preferablyfrom about 1000 to about 2000. Suitable polyether polyols can readily beprepared by polymerizing cyclic ethers, such as tetrahydrofuran, or byreacting one or more alkylene oxides having 2 to 4 carbon atoms in thealkylene radical with an initiator molecule that contains two activehydrogen atoms bound in the alkylene radical. Examples of alkyleneoxides are ethylene oxide, 1,2-propylene oxide, epichlorohydrin and 1,2-and 2,3-butylene oxide. The alkylene oxides may be used individually,alternately in succession or as a mixture. Examples of suitableinitiator molecules are water, glycols, such as ethylene glycol,propylene glycol, 1,4-butanediol and 1,6-hexanediol, amines, such asethylenediamine, hexamethylenediamine and 4,4′-diaminodiphenylmethane,and amino alcohols, such as ethanolamine. Mixtures of initiators can beemployed. The polyether polyols may be used alone or as mixtures. Thepolycarbonate polyols are generally analogous to the polyether polyolsdescribed above, except they are prepared from cyclic carbonates byring-opening of cyclic carbonates or by transcarbonylation reactions ofdialkyl carbonates with one or more polyols, as is well known in theart. Examples of suitable carbonates include ethylene carbonate,1,2-propylene carbonate, 1,3-propylene carbonate, 1,4-butylenecarbonate, 1,3-butylene carbonate, dimethyl carbonate, diethyl carbonateand others known to those skilled in the art. Examples of polyols usefulfor preparation of polycarbonate polyols include the polyols noted belowas polyols suitable for use as the other polyol, as well as the polyolsnoted above for preparation of polyester polyols. Examples of preferredpolyols for use as the other polyol include, diols of 2 to 18,preferably 2 to 10, carbon atoms, for example, 1,2-ethanediol,1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, -1,6-hexanediol,1,10-decanediol, 2-methyl-1,3-propanediol,2-methyl-2-butyl-1,3-propanediol, 2,2-dimethyl-1,3-propane-diol,2,2-dimethyl-1,4-butanediol, 2-ethyl-2-butyl-1,3-propanediol,neopentylglycol hydroxypivalate, diethylene glycol, triethylene glycoland methyldiethanolamine. The diols maybe used individually or asmixtures. Diamines of 2 to 15 carbon atoms, such as ethylenediamine,1,6-hexamethylenediamine, 4,9-dioxododecane-1,12-diamine or4,4′-diamino-diphenylmethane, may also be used. In addition, water canbe in place of or in addition to the other polyol, when, for example, itis desired to make a foam polyurethane. The amount of such other polyolscan be determined by those skilled in the art depending on the desiredproperties of the polyurethane. Advantageously, such other polyols willbe present in an amount from about 0 to 35 weight percent based on thetotal weight of the reactants used to make the polyurethane. Mixtures ofpolyols can be employed.

The methods by which the polyurethanes of the present invention areprepared are not critical. In general, the polyurethanes are made by awell-known polyaddition reaction in which polyfunctionalhydroxyl-containing or amino-containing compounds are allowed to reactwith polyisocyanates.

For example, in the bulk polymerization method, the sulfonate-functionalpolyester polyol, other polyols (if used), and the polyisocyanate arerapidly mixed and heated on a conveyor belt to be polymerized. In themelt polymerization method, the reactants are polymerized while beingkneaded by a single-screw extruder or a multi-screw extruder. Themolecular weight of the polyurethane obtained after being subjected tothe above-described polymerization methods frequently is notsufficiently high. Therefore, the polyurethane thus obtained may befurther subjected to a curing step, also known as solid-phasepolymerization, whereby a thermoplastic polyurethane having the desiredmolecular weight can be obtained. The preferred mixing ratio of thecomponents for the preparation of the thermoplastic polyurethane is setso that the proportion of NCO groups of the polyisocyanate is preferably0.5 to 1.5, and more preferably 0.8 to 1.2, based on the number of totalOH groups, including hydroxyl groups of the sulfonated polyester polyoland hydroxyl groups of the other polyols. Examples of suitable catalystsfor the preparation of the polyurethanes and for the crosslinkingreaction are tertiary amines, such as triethylamine, triethylenediamine,N-methyl-pyridine and N-methylmorpholine, metal salts, such as tinoctanoate, lead octanoate and zinc stearate, and organo-metalliccompounds, such as dibutyltin dilaurate. The suitable amount of catalystis dependent on the activity of the catalyst. Typical catalyst amountsare from 0.005 to 0.3, preferably from 0.01 to 0.1, part by weight per100 parts by weight of polyurethane. The identity and method of use ofcatalysts in the preparation of polyurethanes are well known to thoseskilled in the art.

In a preferred aspect of the invention, thermoplastic polyurethanes areprepared in the absence of a solvent in an extruder. Conventionalextruders that are equipped with one screw or two corotating orcounterrotating screws may be used. Preferred extruders have additionalkneading elements. Suitable extruders include, for example, extruders ofthe ZKS series from Werner & Pfleiderer, Stuttgart, Germany. Theindividual components can be fed to the extruder either in molten formor in solid form, for example as flakes. The reactants can be mixedeither outside the extruder or in the extruder itself. If differentpolyisocyanates are used, they may be premixed. The type and number offeeds and the residence time in the extruder are dependent on thereaction conditions required in each case, for example, on thereactivity of the components, the heat of reaction, etc. The reactiontemperature is in general from about 120 to about 200° C., althoughhigher or lower temperatures can be used. The temperature may be variedduring the reaction; for example, it may be increased in an advantageousmanner from one section of the extruder to the other. The productdischarged from the extruder is advantageously recovered and comminutedin a conventional manner, for example, granulated under water and dried.If required, heating at from about 50 to about 80° C. may follow.

In certain aspects of the invention, for example, thermoplasticpolyurethanes, the polyurethanes prepared according to the invention arepreferably soluble in conventional polar solvents, such as, for example,ethers, such as tetrahydrofuran or dioxane, ketones, such as methylethyl ketone or cyclohexanone, esters, such as ethyl acetate, amides,such as dimethylformamide, or hydrocarbons, such as alkanes oraromatics, or mixtures of solvents.

The polyurethanes of the present invention may be used in a variety ofapplications including, for example, as coatings, adhesives, sealants,waterborne dispersions, foams, fibers, and as dispersants forparticulate materials and/or polar materials. Examples of classes ofparticulate materials include metals and metal oxides, pigments,ceramics, zeolites and molecular sieves. Examples of polar materialsthat may or may not be particulate include dyes, inks, colorants,modifiers, stabilizers, plastizers and reactive diluents. Thepolyurethanes of the present invention may be useful to help bond,stabilize, compatibilize or disperse particulate materials or enhancecompatibility with a coating or other material.

In accordance with the present intention, polyurethanes made using thesulfonate-functional polyester polyols are particularly suitable fordispersing magnetic particles, especially finely divided magneticparticles, as used for magnetic recording systems, for example incomputer data storage tapes, audio tapes or video tapes. Magneticparticles used in magnetic recording systems are also referred to in theart as metal pigments. Compared to commercially available materials, themagnetic dispersions obtained using the polyurethanes of the presentinvention can have better flow properties and the magnetic layersproduced therefrom can have higher gloss values. Moreover, they canprovide good dispersing effect and rapid dispersing, good stabilizationof the dispersion, low solvent requirements in the preparation of thedispersion, good leveling on casting of the dispersion, high pigmentcontent of the magnetic layer, good orientation of the magnetic needlesand good mechanical properties of the magnetic layer, even at hightemperatures.

The polyurethanes of the present invention can be used as the solebinding component for the production of magnetic layers, but it is oftenadvantageous to add at least one further binder component in an amountof less than about 70 percent, preferably less than about 40 percent, byweight, based on the resulting total weight of binder.

A preferred cobinder is a polyvinyl formal binder prepared byhydrolyzing a polymer of a vinyl ester and then reacting the resultingvinyl alcohol polymer with formaldehyde. The polyvinyl binder preferablycontains at least about 65 percent, in particular at least about 80percent by weight, of vinyl formal groups. Particularly suitablepolyvinyl binders contain from about 5 to about 13 percent, by weight,of vinyl alcohol groups and from about 80 to about 88 percent, byweight, of vinyl formal groups and have a density of about 1.2 and aviscosity of from about 50 to 120 millipascals (“mPa”) measured at 20°C. using a solution of 5 g of polyvinyl formal in 100 milliliters (“ml”)of 1:1 (volume) phenol/toluene.

In addition to the polyvinyl formal binders, vinyl chloride/diol mono-or di(meth)acrylate copolymers, which can be prepared, for example, in amanner known in the art by solution copolymerization or suspensioncopolymerization of vinyl chloride and the diol mono(meth)acrylate ordi(meth)acrylate, are also suitable. The preferred diol mono- ordiacrylate or -methacrylate used for this purpose is an esterificationproduct of acrylic acid or methacrylic acid with the corresponding molaramount of aliphatic diol of 2 to 4 carbon atoms, such as ethyleneglycol, 1,4-butanediol and preferably propanediol, the propanediolpreferably comprising about 50 to about 100 percent, by weight, of1,3-propanediol and from about 0 to about 50 percent by weight of1,2-propanediol. The copolymers preferably contain from about 50 toabout 95 percent by weight of vinyl chloride and from about 5 to about50 percent by weight of diol acrylate or diol methacrylate. Particularlysuitable copolymers preferably contain from about 70 to about 90 percentby weight of vinyl chloride and from about 10 to about 30 percent byweight of diol monoacrylate or diol monomethacrylate. A 15 percentsolution of the preferred copolymers, such as the vinylchloride/propanediol monoacrylate copolymers, in a mixture of equalparts by volume of tetrahydrofuran and dioxane, has a viscosity of about30 mPa at 25° C.

In addition, phenoxy resins having repeating units of the formula:

where m is approximately equal to 100, may be used as cobinders. Thesepolymers are commercially available from Inchem Corporation under thetradename Inchemrez™.

Cellulose ester binders are also suitable for use in the binder mixture.These are esterification products of cellulose with nitric acid or withcarboxylic acids of 1 to 4 carbon atoms, for example, cellulose acetate,cellulose triacetate, cellulose acetopropionate or celluloseacetobutyrate.

Typical magnetic materials that may be used include those that influencethe properties of the resulting magnetic layers, such as, for example,gamma-iron (III) oxide, finely divided magnetite, ferromagnetic undopedor doped chromium dioxide, cobalt-modified gamma-iron (III) oxide,barium ferrites or ferromagnetic metal particles. Acicular, inparticular dendrite-free, cobalt-modified or unmodified gamma-iron (III)oxide and ferromagnetic chromium dioxide and metallic pigments such asiron, cobalt, nickel, or alloys thereof are preferred. The particle sizeis in general from 0.01 to 2 micrometers (also referred to as “microns”)preferably from 0.02 to 0.5 microns. The specific surface area is ingeneral at least 40, preferably from 50 to 200 square meters per gram(“m²/g”) determined by the BET method, S. Brunauer, P. H. Emmett and E.Teller, J. Ann. Chem. Soc., 60, 309 (1938).

The ratio of magnetic material to binder is advantageously from about 1to about 10, in particular from about 3 to about 6, parts by weight ofmagnetic material per part by weight of the binder mixture. It isparticularly advantageous that, due to the improved dispersingproperties of the polyurethanes of the present invention, smallermagnetic particles, for example those having an average particle size of0.02-0.05 microns, can be effectively dispersed even at high magneticmaterial concentrations, for example 70 to 90 percent by weight, in themagnetic layers based on the total weight of the magnetic layers,without deterioration of the mechanical-elastic properties or theperformance characteristics.

Moreover, the novel binder compositions may also contain any combinationof crosslinkers, fillers, dispersants, and further additives, such aslubricants, carbon black or nonmagnetic inorganic or organic particulatematerials. The lubricants used may be, for example, carboxylic acids ofabout 10 to about 20 carbon atoms, in particular stearic acid orpalmitic acid, or derivatives of carboxylic acids, such as their salts,esters or amides, or mixtures of two or more thereof.

Examples of suitable nonmagnetic inorganic particulate materials includecarbon black, graphite, metals, metal oxides, metal carbonates, metalsulfates, metal nitrides, metal carbides and metal sulfides, and morespecifically TiO₂ (rutile or anatase), TiO₃, cerium oxide, tin oxide,tungsten oxide, antimony oxide, ZnO, ZrO₂, SiO₂, Cr₂O₃, α-Al₂O₃,β-Al₂O₃, γ-Al₂O₃, α-Fe₂O₃, goethite, corundum, silicon nitride, titaniumcarbide, magnesium oxide, boron nitride, molybdenum sulfide, copperoxide, MgCO₃, CaCO₃, BaCO₃, SrCO₃, BaSO₄, silicon carbide and titaniumcarbide. These compounds may be present either individually or incombination with one another and are not restricted in shape and size.The compounds need not be present in pure form but may have beensurface-treated with other compounds or elements. Organic fillers, suchas polyethylene or polypropylene, may also be used.

The nonmagnetic and nonmagnetizable substrates are not critical andinclude the conventional rigid or flexible substrate materials, inparticular films of linear polyesters, such as polyethyleneterephthalate, in general in thicknesses of from 4 to 200 microns, inparticular from 6 to 36 microns. Recently, the use of magnetic layers onpaper substrates for electronic computing and counting machines has alsobecome important; here too, the binders of the present invention can beadvantageously used.

Magnetic recording media using the polyurethanes of the presentinvention can be produced in any manner known to those skilled in theart. For example, the magnetic pigment dispersion can be prepared in adispersing apparatus, for example a tubular ball mill or a stirred ballmill, from the magnetic material and of the binders with the optionaladdition of lubricants and dispersants. Then, after admixing apolyisocyanate crosslinking agent and optional filtration, thedispersion is applied by means of a conventional coating apparatus, forexample a knife coater, to the nonmagnetic substrate. Advantageously,percent by weight, in the magnetic layers based on the total weight ofthe magnetic layers, without deterioration of the mechanical-elasticproperties or the performance characteristics.

Moreover, the novel binder compositions may also contain any combinationof crosslinkers, fillers, dispersants, and further additives, such aslubricants, carbon black or nonmagnetic inorganic or organic particulatematerials. The lubricants used may be, for example, carboxylic acids ofabout 10 to about 20 carbon atoms, in particular stearic acid orpalmitic acid, or derivatives of carboxylic acids, such as their salts,esters or amides, or mixtures of two or more thereof.

Examples of suitable nonmagnetic inorganic particulate materials includecarbon black, graphite, metals, metal oxides, metal carbonates, metalsulfates, metal nitrides, metal carbides and metal sulfides, and morespecifically TiO₂ (rutile or anatase), TiO₃, cerium oxide, tin oxide,tungsten oxide, antimony oxide, ZnO, ZrO₂, SiO₂, Cr₂O₃, α-Al₂O₃,β-Al₂O₃, γ-Al₂O₃, α-Fe₂O₃, goethite, corundum, silicon nitride, titaniumcarbide, magnesium oxide, boron nitride, molybdenum sulfide, copperoxide, MgCO₃, CaCO₃, BaCO₃, SrCO₃, BaSO₄, silicon carbide and titaniumcarbide. These compounds may be present either individually or incombination with one another and are not restricted in shape and size.The compounds need not be present in pure form but may have beensurface-treated with other compounds or elements. Organic fillers, suchas polyethylene or polypropylene, may also be used.

The nonmagnetic and nonmagnetizable substrates are not critical andinclude the conventional rigid or flexible substrate materials, inparticular films of linear polyesters, such as polyethyleneterephthalate, in general in thicknesses of from 4 to 200 microns, inparticular from 6 to 36 microns. Recently, the use of magnetic layers onpaper substrates for electronic computing and counting machines has alsobecome important; here too, the binders of the present invention can beadvantageously used.

Magnetic recording media using the polyurethanes of the presentinvention can be produced in any manner known to those skilled in theart. For example, the magnetic pigment dispersion can be prepared in adispersing apparatus, for example a tubular ball mill or a stirred ballmill, from the magnetic material and of the binders with the optionaladdition of lubricants and dispersants. Then, after admixing apolyisocyanate crosslinking agent and optional filtration, thedispersion is applied by means of a conventional coating apparatus, forexample a knife coater, to the nonmagnetic substrate. Advantageously,magnetic orientation is carried out before the liquid coating mixture isdried on the substrate; the latter is advantageously effected in thecourse of from about 10 to about 200 seconds at from about 50 to about90° C. The magnetic layers can be calendered and compacted onconventional equipment by being passed between heated and polishedrolls, if necessary with application of pressure and at temperatures offrom about 25 to about 100° C., preferably from about 60 to about 90° C.In the case of crosslinking binders, it is preferred to carry out thecalendering before the crosslinking is complete, since thehydroxyl-containing polymers in the uncrosslinked state are verythermoplastic without being tacky. The thickness of the magnetic layeris in general from about 0.5 to about 20 microns preferably from about 1to about 10 microns. In the case of the production of magnetic tapes,the coated films are slit in a longitudinal direction into theconventional widths.

In a preferred aspect of the present invention, the polyurethane for usein magnetic recording media is a thermoplastic block copolyurethanehaving a block structure in which hard segments B and soft segments Aalternate in the form --A--B--A--B--A--. A thermoplastic blockcopolyurethane may have, for example, a structure A--B--A, where theseindividual blocks are present as separate microphases. The thermoplasticblock copolyurethane has a softening point or a softening range at aspecific temperature or within a specific temperature range. Above thissoftening point or softening range, the polyurethane is plasticallydeformable, said polyurethane retaining the form produced in the plasticstate on returning temperatures below the softening point or softeningrange and behaving essentially like a thermosetting plastic.

In accordance with the present invention, a hard segment (B) desirablyhas a glass transition temperature of at least about 20° C., preferablyat least about 40° C., and more preferably above at least about 50° C.,and a soft segment (A), which is covalently bonded to a hard segment,has a glass transition temperature of less than about 20° C.

In accordance with the present invention, the polyurethane has an anchorgroup including any functional group that is capable of interacting withionic or nonionic, polar compounds. In particular, anchor groups areunderstood as meaning those functional groups that are capable ofinteracting with the surface of inorganic filler materials, inparticular with the surface of inorganic magnetic or magnetizableparticles. According to the present invention, the thermoplastic blockcopolyurethane that can be used in a magnetic recording medium containsat least one sulfonate as an anchor group. Preferably, at least somesulfonate groups are provided by the sulfonate-functional polyesterpolyol. Other functional groups that can serve as anchors include, forexample, carboxyl groups, other sulfo groups, phosphonic acid groups,phosphoric acid groups or salts of such groups.

The polyurethanes of the present invention may have anchor groups eitheronly in one or more soft segments (A) or only in one or more hardsegments (B), or both in one or more soft segments (A) and in one ormore hard segments (B). The number of anchor groups in the soft segments(A) may be greater than the number of anchor groups in the hard segments(B). For example, the ratio of anchor groups in the soft segments (A) tothe number of anchor groups in the hard segments (B) may be from about1000:1 to about 100:1, or less, for example, from about 10:1 to about1.5:1. Conversely, the ratio of anchor groups in the hard segments (B)to the number of anchor groups in the soft segments (A) may likewise befrom about 1000:1 to about 100:1, or less, for example from about 10:1to about 1.5:1.

In a preferred aspect of the invention, the number of anchor groups thatare present in the hard segments (B) of the thermoplastic polyurethaneis greater than the number of anchor groups that are present in the softsegments (A). In a preferred aspect of the invention, the number ofanchor groups that are present in the total number of hard segments (B)present in the polyurethane is at least about five times greater,preferably at least about 10 times greater, than the total number ofanchor groups in the soft segments (A). In a further preferred aspect ofthe invention, the novel thermoplastic polyurethane has essentially noanchor groups in the soft segments (A).

In a preferred embodiment of the invention, the soft segments (A) haveglass transition temperatures of from about −50° C. to about 20° C. In afurther preferred aspect of the invention, the glass transitiontemperatures of the soft segments (A) are from about −30° C. to about 0°C. In order to ensure the desired mechanical properties of thethermoplastic polyurethane, the soft segment (A) desirably has amolecular weight of from about 500 to about 25,000 g/mole. In apreferred aspect of the invention, the soft segment (A) has a molecularweight of from about 1000 to about 10,000, more preferably from about1000 to about 7000, g/mole.

The invention is hereinafter described with reference to the examples,which are not intended to limit the scope of the claims that follow. Allparts and percentages are by weight unless otherwise indicated.

SPECIFIC EMBODIMENTS OF THE INVENTION Example 1 Preparation ofUnsaturated Polyol

A 4-neck glass reaction vessel equipped with a water cooled distillationcondenser, thermocouple and mechanical stirrer and containing 166.7grams of maleic anhydride and 401.8 grams of 1,6-hexanediol under a drynitrogen sparge is heated to 155° C. over 30 minutes. Then, 0.227 ofbutyl tin hydroxide oxide catalyst, sold as Fascat™ 4100, by Elf AtochemNorth America, Inc., Philadelphia, Pa., is added to the reactor. Theheat is increased gradually over 30 minutes to 200° C. and a total of32.37 grams of water collected by distillation.

Example 2 Preparation of Sulfonate-Functional Polyol

The reaction product of Example 1 is allowed to cool down to 111° C. Aclear solution of 176.90 grams of anhydrous sodium bisulfite (NaHSO₃) in420.25 grams of distilled water then ias added to the reaction vessel.The nitrogen sparge is discontinued and the mixture is heated to 80° C.and kept at that temperature for 20 hours. Then, heating of the mixtureis resumed and the temperature raised gradually to 167° C. Above 160°C., the water distilled off and after 2 hours, 393.44 grams of waterdistills overhead. The temperature of the mixture is lowered to 150° C.and it is placed under a vacuum that is gradually decreased to 8 mm Hg.After 15 minutes an additional 11.0 grams of water is distilled. Themixture is discharged at 125-150° C. into a storage container.

Example 3 Preparation of Sulfonate-Functional Polyester Polyol

The reaction product from Example 2 (639.2 grams of it) is placed in a5-liter 4-neck reaction flask and 2392.6 grams of ε-caprolactone (TONE™ECEQ monomer from The Dow Chemical Company) is added to it. The mixtureis heated at 85° C. with stirring under a vacuum of 12 mm Hg with a drynitrogen bleed for 45 minutes to remove water moisture. The mixture isheated over 30 minutes to 140° C. and 9.12 grams of a 1 weight percentsolution of dibutyltin dilaurate (Dabco™ T-12 from Air Products andChemicals, Inc., Allentown, Pa.) in TONE ECEQ monomer is added viasyringe. The consumption of caprolactone is followed throughout thereaction by gas chromatography. The reaction mixture is heated at 140°C. for 24 hours, followed by addition of 0.0934 grams of stannousoctoate catalyst (Dabco T-9). Heating is continued for another 45 hours.The temperature is raised gradually to 160° C. and heated for anadditional 4 hours, at which point the unreacted caprolactoneconcentration (GC) has fallen below 1.0 weight percent. The product isallowed to cool and characterized by titration, showing an acid numberof 0.50 and a hydroxyl number of 52.1 (giving a calculatednumber-average molecular weight of 2154 g/mole). Proton and C-13 NMRanalysis shows peaks consistent with the expected chemical structure.The polydispersity of the polyol (measured by gel permeationchromatography “GPC” analysis) is 1.54.

Example 4 Use of Azeotroping Solvent

This example illustrates the use of an azeotroping solvent to helpremove the water. The first step (preparation of the unsaturated diol)is carried out following the method of Example 1, using the followingraw materials. Maleic Anhydride 402.3 grams 1,6-Hexanediol 968.4 gramsFascat 4100 0.549 grams

The reaction mixture from the first step is allowed to cool to 82° C.and a clear solution of 425.1 grams of anhydrous sodium bisulfite(NaHSO₃) in 1638 grams of distilled water is added to the reactionvessel. The nitrogen sparge is discontinued and the mixture is heated at80° C. for 7 hours followed by 50° C. for 18 hours. The temperature israised gradually over 3 hours to 151° C., whereupon 1570 grams of waterdistills overhead. Toluene (317.6 grams) is added to the reactionmixture, and a Dean-Stark trap and upright condenser are added to theapparatus to collect any remaining water by azeotropic distillation. Themixture is heated to 116° C. and another 42.8 grams of water collectsover 2 hours in the Dean-Stark trap. The temperature is raised to 140°C. and all the toluene is distilled overhead over the course of 2 hours.The reaction mixture is discharged hot from the reaction vessel andallowed to cool.

The reaction product from the previous step (431.1 grams of it) isplaced in a 5-Liter 4-neck reaction flask and 584.07 grams ofε-caprolactone (TONE ECEQ monomer) is added to it. The mixture is heatedat 80° C. with stirring under a vacuum of 20 millimeters (“mm”) Hg witha dry nitrogen bleed for 30 minutes to remove any residual toluene andwater moisture. The mixture is heated over 20 minutes to 140° C. and2.05 grams of a 1 weight percent solution of stannous octoate catalyst(Dabco T-9) in TONE ECEQ monomer is added via syringe. The consumptionof caprolactone is followed throughout the reaction by gaschromatography. The reaction mixture is heated at 140° C. for 20 hoursand another 1.0 grams of 1 percent stannous octoate solution is added.The mixture is heated for an additional 32 hours, at which point theunreacted caprolactone concentration (GC) has fallen below 1.0 weightpercent. The product is discharged from the reactor hot, allowed to cooland characterized by titration, showing an acid number of 0.71 and ahydroxyl number of 103. Proton and C-13 NMR analysis showed peaksconsistent with the expected chemical structure and an approximatenumber-average molecular weight of 1105. The polydispersity of thepolyol by GPC analysis is 1.82.

Example 5 Preparation of Sulfonate-Functional Polyester Polyol

A sulfonated polyester polyol is prepared following the method of thelast step of Example 4 except that the reaction to produce the finalsulfonated polyester polyol is carried out at 160° C. for the entirecourse of reaction, the initial catalyst charge is 3.05 grams of a 1weight percent solution of dibutyl tin dilaurate catalyst (Dabco T-12)in TONE ECEQ monomer, and after 5.5 hours an additional catalyst chargeof 3.05 grams of a 1 weight percent solution of stannous octoatecatalyst (Dabco T-9) in TONE ECEQ monomer is added. These changes resultin a shorter overall reaction time of 25 hours required to produce thesulfonate-functional polyester polyol. The resulting product ischaracterized by titration and shows an acid number of 1.4 and ahydroxyl number of 42.7.

Example 6 Preparation of Sulfonate-Functional Polyester Polyol

A sulfonated polyester polyol is prepared following the method ofExamples 1-3, except that the following amounts of raw materials areused in the first two steps: Maleic Anhydride 147.1 grams 1,6-Hexanediol354.5 grams Fascat 4100 0.200 grams Sodium bisulfite 152.8 grams Water  365 grams

All of the product from the second step is carried on to the third step,where 846.7 grams of ε-caprolactone is used. In this example, only onecatalyst is used in the third step, 8.82 grams of a 1 weight percentsolution of stannous octoate catalyst (Dabco T-9) in TONE ECEQ nonomer.The catalyst is added at the beginning of the reaction after heating to160° C., and a temperature of 160° C. is maintained until the reactionis complete. These conditions result in a shorter reaction time of 22hours, and provide a sulfonate-functional polyester polyol product witha hydroxyl number of 83.5 and an acid number of 0.69.

Example 7 Preparation of Sulfonate-Functional Polyester Polyol

A sulfonated polyester polyol is prepared according to the method ofExample 4, except that no toluene is used. Instead, during theunsaturated diol preparation, 200 grams of Solvesso™ 100 solvent fromExxon Mobil Corporation is added following the addition of the Fascat4100 catalyst to assist in removal of water. The Solvesso 100 is laterremoved by distillation under reduced pressure following removal of thewater at the end of the sulfonated diol preparation step.

Example 8 Complete Preparation Using a Titanium Alkoxide Catalyst

(a) Preparation of Unsaturated Polyol

A 4-neck glass reaction vessel equipped with a thermocouple,water-cooled distillation condenser, and mechanical stirrer andcontaining 73.54 grams of maleic anhydride and 194.39 grams of1,6-hexanediol under a dry nitrogen sparge is heated to 155° C. over 30minutes, and then 0.100 grams of butyl tin hydroxide oxide catalyst(sold as Fascat™ 4100, by Elf Atochem North America, Inc., Philadelphia,Pa.) is added to the reactor. The heat is increased gradually over 30minutes to 20020 C. and a total of 13.09 grams of water is collected bydistillation over the course of two hours. The reaction mixture isallowed to cool to below 100° C. and analyzed by acid number titration,showing an acid number of 0.188.

(b) Preparation of Sulfonate-Functional Polyol

A clear solution of 74.75 grams of anhydrous sodium bisulfite (NaHSO₃)in 182 grams of distilled water is added to the reaction vessel. Thenitrogen sparge is discontinued and the mixture is heated at 80° C. for18 hours. The nitrogen sparge and heating of the mixture is resumed andthe temperature raised gradually to 160° C. The water distills off overthe course of 2 hours, and 162 grams of water is collected. The mixtureis allowed to cool to 150° C. and is placed under partial vacuum. Thepressure is gradually decreased to 9 mm Hg to further dry the reactionmixture for 30 minutes.

(c) Preparation of Sulfonate-Functional Polyester Polyol

The temperature of the reaction mixture is reduced to 85° C. and 432.43grams of ε-caprolactone (TONE ECEQ monomer) is added to it. The mixtureis stirred under a vacuum of 12 mm Hg with a dry nitrogen bleed for 45minutes to remove water. The mixture is heated over 30 minutes to 160°C. and then 2.25 grams of a freshly-prepared 1 weight percent solutionof titanium tetrabutoxide (Tyzor™ TBT from E. I. DuPont de Nemours,Inc., Wilmington, Del.) in TONE ECEQ monomer is added via syringe. Theconsumption of caprolactone is followed throughout the reaction by gaschromatography. The reaction mixture is heated at 160° C. for 5 hours,at which point the unreacted caprolactone concentration (GC) falls below0.5 weight percent. The product is allowed to cool and characterized bytitration, showing an acid number of 0.33 and a hydroxyl number of 115(giving a calculated number-average molecular weight of 976 g/mole).

Example 9 Preparation of Sulfonate-Functional Polyester Polyol

This example illustrates a method whereby a sulfonate-functionalpolyester polyol of higher molecular weight can be obtained from one oflower molecular weight by further reaction with caprolactone.

The sulfonated polyester polyol of Example 4 (170 grams) is placed in a3-liter flask and 1530 grams of ε-caprolactone (TONE ECEQ monomer) areadded. The mixture is heated at 80° C. for 2 hours with stirring andunder a dry nitrogen sparge to remove residual moisture. The mixture isthen heated to 140° C. and 0.32 grams of Fascat 4100 catalyst arecharged to the vessel. The mixture is heated until the unreactedcaprolactone drops below 1 weight percent by gas chromatographicanalysis. The product is then allowed to cool to 110° C. and dischargedinto a storage container. Analysis of the product shows a hydroxylnumber of 9.85, acid number of 0.59, moisture content of 0.25 ppm, a GPCpolydispersity of 2.8 and a Brookfield viscosity at 80° C. (#21 spindleat 1 rpm) of 88,000 centipoise. These data are consistent with theformation of the desired sulfonated polyester polymer of about 10,000number average molecular weight (roughly 10 times that of the startingmaterial before additional caprolactone is added).

Example 10 Preparation of Polyurethane Binder for Mag Media

A 1.5 liter glass reactor fitted with a mechanical stirrer, athermocouple and condenser is charged with 113.6 gram toluenediisocyanate (0.65 mol), 0.3 gram benzoyl chloride and 353.8 gramtetrahydrofuran. The reactor is heated to 50° C. under a N₂ atmosphere.With the aid of a heating mantle and thermocouple (Model PT-100,Eurotherm Ltd., Worthing, West Sussex, UK), the reaction temperature iscontrolled by a Julabo LC1 control unit (Model Julabo LC1, JulaboLabortechnik GmbH, Seelbach, Germany). While stirring vigorously, 0.33mole of a sulfonate-functional polyester polyol as made in accordancewith Examples 1-3 is added slowly to the TDI/THF mixture. The mixture isallowed to react for 4 hours. During the addition and digestion, thecondensor is cooled to −5° C. After digestion, the mixture is collectedfrom the reactor (Product A).

In a another glass reactor (similar to the above), 84.5 gtrimethylolpropane (0.65 mol) and 0.3 g dibutyltin dilaurate aredissolved in 164.2 gram tetrahydrofuran and heated to 50° C. under a N₂atmosphere. While stirring vigorously, Product A is slowly added. Atfrequent intervals during the reaction, infra-red spectra are recorded.The reaction is allowed to proceed until the absorbance associated withthe isocyanate functional group (˜2270 cm-1) is no longer present in themid infra-red spectrum. The total reaction time is approximately 1 hour.After this time, the binder product (Product B) is collected as a 50percent solution in THF.

The Product B is a yellow to brown liquid with an ether smell (due tothe solvent). It has a molecular weight of about 1800 g/mol, determinedby end group analysis (OH titration), and a hydroxyl concentration of3.8 weight percent OH.

Although the invention has been described with respect to specificaspects, those skilled in the art will recognize that the other aspectsare intended to be included within the scope of the claims that follow.For example, more than one species from each class of reactants can beused to make sulfonate-functional polyester polyols, for example, maleicanhydride and fumaric acid, or 1,4-butanediol or 1,6-hexanediol. Theteachings of documents cited herein are incorporated herein byreference.

1. A sulfonate-functional polyester polyol derived from reactantscomprising: (i) an unsaturated polycarboxylic acid or derivativethereof; (ii) a polyol; (iii) a lactone; and (iv) a sulfonating agent:characterized in that the unsaturated polycarboxylic acid or derivativethereof is substantially free of sulfonate functionality.
 2. Thesulfonate-functional polyester polyol of claim 1 having a color of lessthan about
 50. 3. The sulfonate-functional polyester polyol of claim 1wherein the unsaturated polycarboxylic acid or derivative thereof has anaverage concentration of less than about 0.1 equivalent of sulfonatefunctionality per molecule.
 4. The sulfonate-functional polyester polyolof claim 1 wherein the unsaturated polycarboxylic acid or derivativethereof is selected from the group consisting of maleic acid, fumaricacid, itaconic acid, mesaconic acid, citraconic acid, muconic acid,anhydrides of said acids, and any mixture thereof.
 5. Thesulfonate-functional polyester polyol of claim 1 wherein the lactone isepsilon-caprolactone or methyl epsilon-caprolactone.
 6. A polyurethanederived from reactants comprising a polyisocyanate and asulfonate-functional polyester polyol of claim
 1. 7. Asulfonate-functional polyester polyol having the following formula:

where: R¹ is a trivalent hydrocarbon radical having from about 2 toabout 14 carbon atoms; M⁺ is a positively charged counterion; x is fromabout 2 to about 80; n is from about 2 to about 17; and R² is a divalenthydrocarbon radical having from about 2 to about 12 carbon atoms;characterized in that the sulfonate-functional polyester polyol has acolor of less than about
 50. 8. The sulfonate-functional polyesterpolyol of claim 7 having a color of less than about
 25. 9. Thesulfonate-functional polyester polyol of claim 7 having a molecularweight of from about 450 to about 10,000 g/mole.
 10. A process formaking a sulfonate-functional polyester polyol having low color,comprising; (a) reacting an unsaturated polycarboxylic acid orderivative thereof with a polyol to form an unsaturated polyol; saidunsaturated polycarboxylic acid or derivative thereof beingsubstantially free of sulfonate functionality; (b) reacting theunsaturated polyol with a sulfonating agent to form asulfonate-functional polyol; and (c) reacting the sulfonate-functionalpolyol with a lactone to provide the sulfonate-functional polyesterpolyol.